The Impact of Polydispersity and Molecular Weight on the Order–Disorder Transition in Poly(3-hexylthiophene)

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Panzer, Fabian ; Bässler, Heinz ; Lohwasser, Ruth ; Thelakkat, Mukundan ; Köhler, Anna:
The Impact of Polydispersity and Molecular Weight on the Order–Disorder Transition in Poly(3-hexylthiophene).
In: The Journal of Physical Chemistry Letters. Vol. 5 (2014) Issue 15 . - pp. 2742-2747.
ISSN 1948-7185
DOI: https://doi.org/10.1021/jz5009938

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Abstract in another language

Conjugated poly(3-hexylthiophene) (P3HT) chains are known to exist at least in two distinct conformations: a coiled phase and a better ordered aggregated phase. Employing steady state absorption and fluorescence spectroscopy, we measure the course of aggregation of P3HT in tetrahydrofuran (THF) solution within a temperature range of 300 K to 170 K. We show that aggregation is a temperature controlled process, driven by a thermodynamic order–disorder transition. The transition temperature increases with the molecular weight of the chains and can be rationalized in the theory of Sanchez. This implies a smearing out of the phase transition in samples with increasing polydispersity and erodes the signature of a first order phase transition. The detection of a hysteresis when undergoing cooling/heating cycles further substantiates this reasoning.